1. Technical Field
The present disclosure relates to carbon nanotube structures, methods for making the same and field emission devices using the same.
2. Description of Related Art
Carbon nanotubes produced by means of arc discharge between graphite rods were first discovered and reported in an article by Sumio Iijima, entitled “Helical Microtubules of Graphitic Carbon” (Nature, Vol. 354, Nov. 7, 1991, pp. 56-58). Carbon nanotubes also feature extremely high electrical conductivity, very small diameters (much less than 100 nanometers), large aspect ratios, and a tip-surface area near the theoretical limit. These features tend to make carbon nanotubes ideal candidates for electron emitter in field emission device.
In US20060192475A1 published on Aug. 31, 2006, Li et al. discloses a carbon nanotube emitter and its fabrication method. The carbon nanotube emitter includes a plurality of first carbon nanotubes arranged on a substrate and in parallel with the substrate, and a plurality of the second carbon nanotubes arranged on a surface of the first carbon nanotubes. The method for making the carbon nanotube emitter includes: growing a plurality of first carbon nanotubes on a first substrate having a catalyst material layer arranged thereon; separating the first carbon nanotubes from the first substrate and immersing the first separated carbon nanotubes in a dispersion solution; coating a second substrate with the dispersion solution and baking the second coated substrate at a predetermined temperature to fix the first carbon nanotubes on the second substrate and in parallel with the second substrate; and growing a plurality of second carbon nanotubes from a plurality of nano catalyst particles on the surface of the first carbon nanotubes.
However, the method for making the carbon nanotube emitter is complicated and the combination force between the first carbon nanotubes and the second carbon nanotubes are week. Thus, the carbon nanotubes of the carbon nanotube emitter are easy to be pulled out when it is used in field emission device.
What is needed, therefore, is to provide a carbon nanotube structure in which the carbon nanotubes are firmly fixed and not easy to be pulled out, and a simple method for making the same.